FIGURE 2.

Post-translational procession of prelamin A, B1, and B2. (A) Post-translational procession of prelamin A to lamin A. Prelamin A undergoes four post-translational chemical reactions before the mature lamin A is formed. Step I, the farnesyltransferase mediates farnesylation of the CAAX motif of prelamin A. Step II, the last tripeptide is clipped off by ZMPSTE24 or RCE1. Step III, ICMT methylates the exposed farnesylated cysteine residue. Step IV, removal of the last 15 amino acid residues by ZMPSTE24, including the C-terminal farnesylcysteine methyl ester. (B) Lamin C does not undergo these processing steps as it does not contain the CAAX motif. The mature lamins B1 and B2 remain permanently farnesylated at their C-termini.